Fuel supply pump

ABSTRACT

A fuel supply pump, which is simple in construction and easy to produce and is capable of efficiently pressurizing a high flow rate of fuel, is provided. The fuel supply pump ( 50 ) includes a housing ( 52 ), a plunger barrel ( 53 ), a plunger ( 54 ) for pressurizing fuel, which is installed in the plunger barrel ( 53 ) so as to be allowed to move up and down, a cam ( 60 ) installed in rotation way below the plunger ( 54 ), a tappet structure body ( 6 ) installed between the cam ( 60 ) and the plunger ( 54 ) to transmitting the turning force, serving as a lifting force, from the cam shaft ( 3 ) to the plunger ( 54 ), a tappet structure body ( 6 ) installed between the cam ( 60 ) and the plunger ( 54 ) and provided for transmitting a upward or downward movement of the cam ( 60 ) caused by the rotation of the camshaft ( 3 ) to the plunger ( 54 ); and a return spring ( 68 ) for setting lowering force to the plunger ( 54 ), which is installed between the tappet structure body ( 6 ) and the plunger barrel ( 53 ).

TECHNICAL FIELD

The present invention relates to a fuel supply pump. Particularly, thepresent invention relates to a fuel supply pump suitable for anaccumulator fuel injection device with a pressure-amplifying piston(APCRS: Amplified Piston Common Rail System) that requires a high flowrate of pressurized fuel.

BACKGROUNDS

A conventional fuel supply pump 250 has been constructed as shown inFIG. 16. The conventional fuel supply pump 250 comprises: a pump housing252 having a cylindrical space opened from end to end in the verticaldirection; a plunger barrel 253 installed in the upper opening portionof the pump housing 252; a plunger 254 for pressurizing fuel, which isinstalled in the plunger barrel 253 and the cylindrical space of thepump housing 252 so as to be allowed to move up and down; a cam 260installed in a rotation way below the plunger 254 and integrated with acam shaft 3 (not shown) inserted into the pump housing 252 in thelongitudinal direction; a tappet structure body installed between thecam 260 and the plunger 254 and provided for transmitting the torque ofthe cam shaft 203 as a lifting force to the plunger 254; and a returnspring 268 for setting lowering force to the plunger 254, which isinstalled between the tappet structure body 206 and the plungerbarrel-253.

As disclosed in JP 2001-317430 A and JP 2001-221130 A, such aconventional fuel supply pump 250 is constructed so as to move the cam260 up and down when the cam shaft 3 is revolved by driving an engine(not shown). In conjunction with such a movement, the plunger 254 isallowed to be lifted and lowered through the tappet structure body 206.Therefore, the fuel supply pump 250 is constructed such that fuel can besuctioned into a pump chamber through an inlet valve by lowering theplunger 254, while the fuel in the pump chamber can be pressurized bylifting the plunger 254 to discharge the fuel from the pump chamber to apressure-accumulating chamber (not shown) through an outlet valve.

However, such a fuel supply pump is provided with a projection 252 a forsupporting the upper end of the return spring 268 in the innerperipheral surface of the pump housing 252. Thus, for assembling thefuel supply pump 250, the plunger barrel 253 and the plunger 254 have tobe inserted into the accommodating portion of the pump housing 252 fromthe upper portion thereof while staying out of the projection 252 a. Onthe other hand, the return spring 268 and the tappet structure body 206have to be inserted from a floor plug 280 formed below the pump housing252 while staying out of the projection 252 a. Consequently, in theconventional fuel supply pump, there are problems in that the assemblywork is complicated and the production cost is not easily reduced.

Furthermore, for a diesel engine, as disclosed in JP 56-93936 A and JP2885076 B, an accumulator fuel injection device (CRS: Common RailSystem) that employs an accumulator (common rail) has been proposed tomake it possible to increase engine power, improve fuel consumption,reduce particulate matters, and so on by efficiently injectinghigh-pressure fuel. There has been also proposed an accumulator fuelinjection device that pressurizes and utilizes fuel from an accumulator.

Such a fuel supply pump 250 is intended to supply a relatively high flowrate of fuel into the accumulator by providing a predeterminedlubrication mechanism (not shown) in a tappet structure body and forminga seal ring 252 b installed between a pump housing 252 and a plungerbarrel 253 into a predetermined shape. However, the degree ofpressurization and the flow rate of fuel are still insufficient to allowhigher power of the diesel engine.

Therefore, as a result of concentrated study, the present inventors havefound out that the above problem can be solved by forming a projectionon the plunger barrel to retain the upper end of a return spring,instead of forming a projection for supporting the upper end of thereturn spring on the inner peripheral surface of a pump housing.

That is, an object of the present invention is to provide a fuel supplypump, which is not only simple in construction and easy to produce butalso capable of efficiently pressurizing a high flow rate of fuel.

DISCLOSURE OF THE INVENTION

[1] According to the present invention, the above object can be solvedby providing a fuel supply pump comprising: a pump housing having acylindrical space opened from end to end in the vertical direction; aplunger barrel installed in the upper opening portion of the pumphousing; a plunger for pressurizing fuel, which is installed in theplunger barrel and the cylindrical space of the pump housing so as to beallowed to move up and down; a cam installed in rotation way below theplunger and integrated with a cam shaft inserted into the pump housing;a tappet structure body installed between the cam and the plunger andprovided for transmitting a upward or downward movement of the camcaused by the rotation of the cam shaft to the plunger; and a returnspring for setting lowering force to the plunger, which is installedbetween the tappet structure body and the plunger barrel, wherein theplunger barrel has a projection for supporting the upper end of thereturn spring.

That is, as constructed above, the inner peripheral surface of the pumphousing does not require a projection for supporting the upper end ofthe return spring. Thus, no obstacle is provided on the inner peripheralsurface of the pump housing has, so that the respective structuralcomponents such as the tappet structure body, the plunger barrel, andthe plunger can be temporarily preassembled and inserted into thecylindrical space of the housing from the upper portion of the pumphousing. In addition, no floor plug for inserting the tappet structurebody is required. Consequently, the fuel supply pump simple inconstruction and easy to produce can be provided.

Furthermore, there is no obstacle in the inner peripheral surface of thepump housing, so that the inner peripheral surface of the pump housingcan be processed more precisely and more easily than a conventional one.Thus, the cam shaft can be set at a higher rotational frequency.Consequently, the fuel supply pump, which is capable of supplying a highflow rate of fuel sufficiently pressurized into an accumulator, can beprovided.

[2] For the configuration of the fuel supply pump of the presentinvention, it is preferred that the plunger barrel has a large diameterportion for restricting the movement of the return spring in the radialdirection.

As configured above, the fuel supply pump of the present invention doesnot require any of projections and other restricting componentsconventionally provided in the inner peripheral surface of the pumphousing for restricting the movement of the return spring in the radialdirection.

Thus, the number of components can be reduced. Consequently, the fuelsupply pump, which is simple in construction and easy to produce, can beprovided.

[3] Furthermore, for the configuration of the fuel supply pump of thepresent invention, it is preferred that the projection of the plungerbarrel has an outer peripheral surface fitted to the peripheral surfaceof the cylindrical space of the pump housing.

As configured above, the movement of the plunger barrel in the radialdirection within the pump housing can be restricted easily andprecisely.

[4] Additionally, for the configuration of the fuel supply pump of thepresent invention, it is preferred that the plunger barrel has a sealring receiver in the outer peripheral surface of the projection.

As configured above, the movement of the plunger barrel in the radialdirection within the pump housing can be restricted more effectively.

[5] In addition, for the configuration of the fuel supply pump of thepresent invention, it is preferable to provide a spring sheet betweenthe return spring and the tappet structure body. The spring has anopening portion into which the plunger is inserted. In this case, aspring holding portion for restricting the downward movement of thereturn spring is also provided in the outer peripheral portion of thespring sheet.

As configured above, the return spring is allowed to exert spring forceas lowering force effectively work on the plunger through the springsheet.

[6] Additionally, for the configuration of the fuel supply pump of thepresent invention, it is preferred that the tappet structure bodyfurther comprises a cylindrical shell having an outer peripheral surfacefitted to the peripheral surface of the cylindrical space of the pumphousing, wherein the inner surface of the shell is provided with aprojection for restricting the movement of the return spring in theradial direction.

As configured above, a roller body itself is not required to have afunction for restricting the movement of the spring sheet in the radialdirection. Thus, the composition of the roller body can be simplified.

[7] Furthermore, for constructing the fuel supply pump of the presentinvention, it is preferable to use an accumulator fuel injection devicefor pressurizing fuel having a flow rate per unit time of 500 to 1,500litters per hour up to 50 MPa or more.

Using such an accumulator fuel injection device, the pressurization ofthe fuel having a large flow rate can be easily carried out. Therefore,the accumulator fuel injection device attains a further increase in fuelefficient, so that a diesel engine will have a higher power and anincrease in fuel consumption, while attaining a reduction in particulatematters, and so on.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a side-view of the fuel supply pump of the present inventionwith a portion partly broken away.

FIG. 2 is a cross-sectional view of the fuel supply pump of the presentinvention.

FIG. 3 is a diagram with perspective and cross-sectional views of ahousing.

FIG. 4 is a diagram for illustrating a plunger barrel, a fuel inletvalve, and a fuel outlet valve.

FIG. 5 is diagram with perspective and cross-sectional views of aplunger.

FIG. 6 is a diagram with perspective, plane, and cross-sectional viewsof a spring sheet.

FIG. 7 is a diagram for illustrating a tappet structure body.

FIG. 8 is a diagram for illustrating a roller body.

FIG. 9 is a perspective view of the tappet structure body.

FIG. 10 is a cross-sectional view of the fuel inlet valve.

FIG. 11 is a cross-sectional view of the fuel inlet valve.

FIG. 12 is a diagram for illustrating the system of an accumulator fuelinjection device (APCRS) in the form of a pressure amplifying pistonsystem.

FIG. 13 is a diagram for illustrating the configuration of theaccumulator fuel injection device (APCRS) in the form of a pressureamplifying piston system.

FIG. 14 is schematic diagram for illustrating a method for raising thepressure of fuel in the accumulator fuel injection device (APCRS) in theform of a pressure amplifying piston system.

FIG. 15 is a diagram for illustrating a timing chart of high-pressurefuel injection.

FIG. 16 is a diagram for illustrating the configuration of aconventional fuel supply pump.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the fuel supply pump will be described concretely withproper references to the drawings.

1. Basic Configuration of Fuel Supply Pump

As shown in FIG. 1 and FIG. 2, the present embodiment is a fuel supplypump 50 comprising: a pump housing 52 having a cylindrical space openedfrom end to end in the vertical direction; a plunger barrel 53 installedin the upper opening portion of the pump housing 52; a plunger 54 forpressurizing fuel, which is installed in the plunger barrel 53 and thecylindrical space of the pump housing 52 so as to be allowed to move upand down; a cam 60 installed in rotation way below the plunger 54 andintegrated with a cam shaft 3 inserted into the pump housing 52; atappet structure body 6 installed between the cam 60 and the plunger 54and provided for transmitting a upward or downward movement of the cam60 caused by the rotation of the cam shaft to the plunger 54; and areturn spring 68 for setting lowering force to the plunger 54, which isinstalled between the tappet structure body 6 and the plunger barrel 53.

In addition, for the fuel supply pump 50 of the present embodiment, theplunger barrel 53 has a projection 53 a for supporting the upper end ofthe return spring 68.

Hereinafter, the fuel supply pump 50 will be described more concretelyby way of individually describing its structural components.

(1) Pump Housing

As exemplified in FIG. 1 and FIG. 2, the pump housing 52 is provided asan enclosure for housing the plunger barrel (cylinder) 53, the plunger54, the tappet structure body 6, and the cam 60, and also provided forcompartmentalizing the fuel compression chamber 74. Therefore,preferably, as shown in FIG. 3(a) and 3(b), the pump housing 52 has ashaft-inserting hole 92 a opened from side to side in the horizontaldirection and a cylindrical spaces 92 b, 92 c opened from end to end inthe vertical direction.

Furthermore, as shown in FIG. 3(b), the pump housing 52 is preferablyprovided with through-holes 97, 98 opened in the lateral directions ofthe cylindrical spaces 92 b, 92 c, respectively. Specifically, each ofthe through-holes 97, 98 is preferably provided as an assembly of threehole portions (large, middle, and small holes) 97 a-97 c, 98 a-98 c withdifferent pore sizes, concentrically arranged in a stepwise pattern.Therefore, the tip portions of guide pins (not shown) are press-insertedinto the hole portions 97 a, 98 a to ensure high-precision positioningof the guide pins. In addition, the hole portions 97 b, 98 b have theirown functions of introducing the tip portions of the guide pins into thehole portions 97 c, 98 c to press-insert the tip portions of the guidepin into the hole portions 97 c or 98 c, respectively. In addition, thehole portions 97 a, 98 a are preferably formed of threaded portions suchthat the guide pins can be press-fitted into the hole portions 97 a, 98a to press-insert the dip portions of the guide pins into the holeportions 97 a, 98 a, respectively. Therefore, the guide pin can bepress-inserted by means of thread engagement.

Furthermore, because the projection for supporting the upper end of thereturn spring 68 is provided in the plunger barrel 53 described below,projections in the inner peripheral surface of the cylindrical spaces 92b and 92 c in the pump housing 52 are not required.

Thus, the inner peripheral surface of the pump housing 52 can beprocessed easily and precisely. Thereby, even in the case of rotatingthe cam shaft 3 at high speed, the vibration by the rotation can beeffectively controlled. Consequently, the cam shaft 3 can be set at ahigher rotational frequency than a conventional one. Furthermore, highpower of a diesel engine, improvement in fuel consumption, reduction inparticulate matters, and so on can be attained because the cam shaft 3can be rotated at high speed and a high flow rate of fuel sufficientlypressurized can be supplied into an accumulator. In addition, there isno need to arrange a floor plug for inserting the tappet structure bodyand so on, allowing simpler composition.

Moreover, the fuel supply pump 50 can be assembled by only temporarilypreassembling each component such as the tappet structure body 6, theplunger barrel 52, and the plunger 54 and inserting them into thecylindrical spaces 92 b and 92 c of the housing from the upper portionof the pump housing 52. Thus, the production cost can be significantlyreduced.

Still, it is preferable that the movement of the return spring 68 in theradial direction is restricted by the plunger barrel 53. This is becauseof no need of any spring receiver that is conventionally essential torestrict the movement of the return spring in the radial direction.Therefore, the inner peripheral surface of the pump housing can beprocessed more easily and precisely. As a result, the cam shaft can beset at a higher rotational frequency.

(2) Plunger Barrel

A plunger barrel 53 is, as exemplified in FIG. 1 and FIG. 2, anenclosure for supporting the plunger 54 and constitutes a part of a fuelcompression chamber (pump chamber) 74 for pressurizing a large amount offuel at high pressures by the plunger 54. Therefore, the plunger barrel53 is attached to the upper opening portion of each of the cylindricalspaces 92 b, 92 c in the pump housing 52. In addition, as shown in FIG.2, the fuel compression chamber 74 for compressing the fuel introducedfrom a fuel tank (not shown) is installed between the outer peripheralsurface of the plunger barrel 53 and the inner peripheral surface of thepump housing 52 (the peripheral surface of the cylindrical spaces 92 band 92 c).

Furthermore, the plunger barrel 53 is characterized by having theprojection 53 a for supporting the upper end of the return spring 68. Itis because of no need of any projection to restrict the upward movementof the return spring 68 in the inner peripheral surface of the pumphousing 52 as the upper end of the return spring 68 is supported by theprojection 53 a of the plunger barrel 53.

Moreover, as shown in FIG. 2, the plunger barrel 53 is preferablyprovided with a large diameter portion 53 b for restricting the movementof the return spring 68 in the radial direction. It is because of noneed of any projection to restrict the movement of the return spring 68in the radial direction in the peripheral surface of the pump housing 52as well as to provide any component between the pump housing 52 and thereturn spring 68 to restrict the movement of the return spring 68 in theradial direction.

In addition, preferably, for the plunger barrel 53, the projection 53 ahas an outer peripheral surface fitted to the peripheral surface of thecylindrical space of the pump housing 52. This is because the movementof the plunger barrel 53 in the radial direction within the pump housing52 can be restricted.

Furthermore, for the plunger barrel 53, as shown in FIG. 4, the outerperipheral surface of the projection 53 a is preferably provided with aseal ring receiver 53 c. This is because the movement of the plungerbarrel 53 in the radial direction within the pump housing 52 can berestricted more effectively.

Furthermore, regarding the conformation of the plunger barrel 53, whenthe fuel supply pumps to be mounted on the plunger barrel are of inlineand radial types, the conformation of the plunger barrel can be suitablychanged so as to correspond to the respective types.

(3) Plunger

As exemplified in FIG. 1 and FIG. 2, the plunger 54 is a principlestructural component for pressurizing fuel at high pressures in the fuelcompression chamber 74 formed in the plunger barrel 53. Therefore, theplunger 54 is arranged so as to be capable of lifting and loweringmovements in the plunger barrel 53 attached in each of the cylindricalspaces 92 b, 92 c formed in the pump housing 52 lifting and lowermovement. In addition, as shown in FIG. 1 and FIG. 2, the plunger 54 isprovided with a pressure portion 54 a for allowing the plunger 54 to beintroduced into or pulled out of the inside of the fuel compressionchamber 74.

The pressure portion 54 a is designed such that the pressure portion 54a has a diameter smaller than the diameter of the plunger barrel 53.Thus, a gap is preferably formed between the pressure portion 54 a andan outlet valve 79 when the pressure portion 54 a moves to the top deadcenter. This is because that the plunger 54 is driven at high speed tosmoothly feed fuel to a common rail under pressure without allowing thepressure portion 54 a to occlude the inlet of the outlet valve 79 evenafter pressurizing a large amount of fuel.

Furthermore, the plunger 54 is preferably formed in the shape of a roundbar as a whole and provided with a collar portion 55 on its opposite endwith respect to the pressure portion 54 a to allow the plunger 54 to besmoothly driven at high speed. That is, it is preferable that the collarpart 55 for locking is integrally formed on the external peripheralsurface of the tip portion (lower end portion) of the cylindricalplunger 54. This is because that such a configuration of the plunger 54can be easily and positively fixed in the opening portion 15 formed inthe plunger mounting portion 14.

Furthermore, as shown in FIG. 2, the plunger 54 is preferablyconstructed such that the plunger 54 is always forced to move toward thecam by a spring 68 for returning the plunger and moves upward inresponse to the rotary movement of the cam 60 to pressurize fuel in thefuel compression chamber 74.

Furthermore, in the fuel supply pump of the present embodiment, it ispreferable to pressurize a large amount of fuel by driving the cam andthe plunger at high speed in the plunger barrel 53. Specifically, therotation frequency of the cam is preferably in the range of 1,500 to4,000 rpm. In addition, considering a gear ratio, the rotation frequencyof the cam is preferably in the range of 1 to 5 times higher than therotation frequency of an engine.

(4) Fuel Compression Chamber

As shown in FIG. 2, the fuel compression chamber 74 is a small chamberin the plunger barrel 53, which is formed by a combination of theplunger barrel 53 and the plunger 54. Thus, in the fuel compressionchamber 74, the fuel quantitatively introduced into the fuel compressionchamber 74 through a fuel inlet valve 73 can be pressurized efficientlyand massively by driving the plunger 54 at high speed. Furthermore, eventhough the plunger 54 is driven at high speed as described above, forpreventing a fuel for lubrication from inhibiting a high speed movementof the plunger 54, it is preferable that a spring sheet and a rollerbody described latter are provided with their respective fuelpass-through holes and the corresponding fuel pass-through holes arecommunicated with each other.

On the other hand, after completion of pressurization with the plunger54, the pressurized fuel is supplied to a common rail (not shown)through the fuel outlet valve 79.

(5) Spring Sheet

FIG. 6(a) is a perspective view of the spring sheet 10. Similarly, FIG.6(b) is a plane view of the spring sheet 10 and FIG. 6(c) is across-sectional view of the spring sheet 10 shown in FIG. 16(a).

The spring sheet 10 comprises a spring holding portion 12 for supportinga spring to be used at the time of pulling down the plunger 54 of thefuel supply pump 50 and a plunger mounting portion 14 for catching theplunger. Preferably, pass-through holes 16 for allowing passage of alubricant or a fuel for lubrication are formed around the plungermounting portion 14. In addition, for the spring sheet 10, an openingportion 15 for penetrating the plunger 54 there into is preferablyprovided in the center of the plunger mounting portion 14. This isbecause, as constructed above, a lubricant or a fuel for lubrication canmove forward and backward freely through the spring sheet 10.Consequently, factors for inhibiting the plunger 54 driven at high speedare allowed to be lessened.

(6) Tappet Structure Body

Next, the tappet structure body will be described with reference to thedrawings. Here, FIG. 7 is a diagram for illustrating the tappetstructure body. Similarly, FIG. 8 is a diagram for illustrating a rollerbody and FIG. 9 is a perspective view of the tappet structure body.

As shown in (a) to (c) of FIG. 7, the tappet structure body 6 isconstructed of a roller 29 in which a pin portion and a roller portionare integrated together, the roller body 28 receiving the roller 29, anda cylindrical shell 27 arranged so as to surround the roller 29 and theroller body 28. Preferably, it is constructed so as to be lifted andlowered by the rotary movement of the cam shaft 3 and the cam 60connected thereto shown in FIG. 1.

This is because, as constructed above, the number of components can besaved and the conventional lubrication between the pin and the roller isnot required. Thus, the roller is allowed to be driven at high speed.Consequently, because the cam shaft 3 can be set at a higher rotationalfrequency, a high flow rate of fuel that is sufficiently pressurized canbe supplied into an accumulator.

In addition, as shown in FIGS. 7(a) to 7(c), the roller body 28preferably has a main body 30 and is then held within the shell 27.Furthermore, on the main body 30, the roller support 30 a having theinner peripheral surface is fitted to the outer peripheral surface ofthe roller 29. As shown in FIGS. 8(a) to 8(c), on the central portion ofthe upper surface of the main body 30, a contact portion 30 c isprovided integrally with the plunger 54 and protrudes toward the plunger54. Preferably, on the peripheral portion of the main body 30, a sheetreceiver 30 d for receiving the spring sheet 10 is provided integrallytherewith to protrude.

On the other hand, preferably, the surface of the roller receiver 30 ais formed with a carbon coating consisting of an amorphous hard carbonfilm. This is because the friction against the surface of the rollerreceiver 30 a is reduced and the abrasion on the surface of the rollerreceiver 30 a is prevented. Thus, the roller 29 is allowed to be drivenat high speed.

Still, the carbon coating preferably contains nitrogen and silicon.Also, preferably, its formation method utilizes, but not particularlylimited to, a CVD method with plasma and ion beam.

In addition, as illustrated in FIG. 7 to FIG. 9, for the roller body 28,for example two fuel pass-through holes 30 b through which a lubricantused for lubricating the inner portion of the fuel supply pump or fuelis passed are preferably arranged around the roller body at thesymmetric position with respect to a central projection 30 c.

Preferably, the shell 27 opens from end to end in the vertical directionand forms a cylindrical body having an outer peripheral surface fittedto the peripheral surface of cylindrical spaces 92 b and 92 c of a pumphousing 52 shown in FIG. 3. Furthermore, on the top of the peripheralwall of the shell 27, a long hole 27 a into which the guide pin isinserted is provided and formed as a pass-through hole extending in theaxis direction of the shell 27. This is because the guide pin and thelong hole 27 a cooperate to be capable of moving up and down along theaxis of the cylindrical spaces 92 b and 92 c for maintaining themovement of the tappet structure body 6 in the required direction, whenthe tappet structure body 6 moves up and down. Moreover, centering thetappet structure body 6 on the pump housing 52 can be performed only byinserting the outer peripheral surface of the shell 27 into the pumphousing 52.

Additionally, the inner peripheral surface of the shell 27 is preferablyprovided with a first projection 27 b as a projection for restrictingthe upward movement of the roller body 28. Similarly, the innerperipheral surface of the shell 27 is provided with a second projection27 c integrally therewith as a projection for restricting the movementof the spring sheet 10 in the radial direction. This is because theroller body 28 is not required to have a function for restricting themovement of the spring sheet 10 in the radial direction. Thus, theroller body 28 is allowed to be simplified in construction.

(7) Cam

As shown in FIG. 1 and FIG. 2, a cam 60 is a main element for convertingthe rotary movement of a motor into the vertical motion of the plunger54 through the tappet structure body 6. Therefore, preferably, the cam60 is inserted in rotation and held in a shaft-inserting hole 92 a via abearing body. Then, it is constructed so as to be revolved by driving anengine (cam shaft 3).

The cam 60 is preferably integrally provided with two cam portions 60 inparallel with each other with a predetermined distance in the axialdirection with respect to the cam shaft 3 and located below thecylindrical space 92 of the pump housing 52.

(8) Fuel Inlet Valve and Fuel Outlet Valve

Preferably, a fuel inlet valve and a fuel outlet valve are arranged asexemplified in FIG. 4 and constituted as exemplified in FIGS. 10 to 11.

In other words, as shown in FIG. 10, the fuel inlet valve 73 ispreferably constructed of a valve main body 19 and a valve body 20having a collar portion 20 b on its tip portion. Besides, as shown inFIG. 10, the valve main body 19 is preferably provided with acylindrical fuel inlet chamber 19 a opened downward and a fuel inlethole 19 b for feeding fuel into the fuel inlet chamber 19 a.

Furthermore, preferably, the fuel outlet valve 79 comprises a valve bodyand is housed in part of the pump housing.

Then, preferably, the valve body is always energized by a spring in thevalve-closing direction to supply a pressurized fuel to a common rail byopening and closing the valve.

Furthermore, as shown in FIG. 11, each of the fuel inlet valve 73 andthe fuel outlet valve 79 comprises the valve main body 19, the valvebody 20 movably attached in the inside of the valve main body 19, thefuel inlet chamber 19 a provided in the inside of the valve main body19, the fuel inlet hole 19 b, the sheet portion 23 mutually contactedwith the valve body 20 and part of the valve main body 19. Preferably,two or more fuel inlet holes 19 b are formed and arranged in anon-radial pattern with respect to the fuel inlet chamber 19 a.

This is because that such a fuel inlet valve supplies the fuel supplypump with fuel, for example, even at a flow rate of approximately 500 to1,500 litters per hours quickly and quantitatively.

Likewise, the fuel outlet valve as constructed above also supplies thecommon rail with fuel, for example, even at a flow rate of approximately500 to 1,500 litters per hours quickly and quantitatively.

(9) Lubrication System

Furthermore, a lubrication system of the fuel supply pump preferablyemploys, but not specifically limited to, a fuel lubrication system thatutilizes part of a fuel oil as a lubrication component (fuel forlubrication).

This is because, when fuel is pressurized and fed under pressure intothe common rail, particular problems are not generated because of usingfuel for lubricating the cam chamber and so on, even though part of thefuel for lubricating the cam chamber and so on would be mixed with thefuel fed under pressure into the common rail. That is, because they havethe same composition, there is no chance that additives and so oncontained in a lubricant is mixed with the fuel fed under pressure intothe common rail, unlike the lubricant used for lubricating the camchamber and so on. Therefore, employing the fuel lubrication systemprevents additive and so on contained in a lubricant from being mixedwith fuel and injected into an engine. As a result, the exhaust gaspurification is not allowed to be lowered.

2. Amplified Piston Common Rail System

Furthermore, the fuel supply pump of the present embodiment ispreferably a part of a piston amplifying mechanical common rail system(APCRS) 100.

That is, as shown in FIG. 12, the fuel supply pump 103 is preferablyconstructed of a fuel tank 102, a feed pump (low pressure pump) 104 forsupplying the fuel from the fuel tank 102, a fuel supply pump (highpressure pump) 103, a common rail 106 provided as a pressure accumulatorfor pressure-accumulation of the fuel fed under pressure from the fuelsupply pump 103, a piston amplifier 108 (pressure amplifying piston),and a fuel injection system 166.

(1) Feed Pump and Fuel Supply Pump

The feed pump 104 is, as shown in FIG. 12, provided for feeding fuel(diesel oil) in the fuel tank 102 to the fuel supply pump 103 underpressure. It is preferable that a filter 105 is placed between the feedpump 104 and the fuel supply pump 103.

Preferably, the feed pump 104 has a gear pump structure mounted on theend of the cam shaft such that the feed pump 104 can be driven bydirectly connecting with the axis of the cam shaft or through anappropriate gear ratio.

Furthermore, the fuel fed under pressure from the feed pump 104 throughthe filter 105 is preferably supplied to the fuel supply pump 103through a proportional control valve (FMU) 120 known in the art.

This proportional control valve can regulate the fuel fed to an inletvalve (not shown) of the fuel supply pump 103 under the control of thelater-described electrical controlling unit (ECU).

In addition to feed the fuel supplied from the feed pump 104 to theproportional control valve 120 and the fuel supply pump 103 underpressure, it is preferable to construct that the fuel is returned to thefuel tank 102 through a overflow valve (OFV) 134 installed in parallelwith the proportional control valve 120. Moreover, it is preferable thatpart of the fuel is fed under pressure to a bearing (not shown) of thefuel supply pump 103 and then used as a fuel lubricating oil of thebearing.

By the way, the fuel supply pump 103 is a device for pressurizing thefuel supplied from the feed pump 104 at high pressure as describedabove. The fuel supply pump 103 is preferably constructed such that,after pressurizing the fuel, the fuel is fed to the common rail 106under pressure through the high pressure channel 107.

(2) High Pressure Path

Furthermore, as shown in FIG. 12, it is preferable to install a one wayvalve (not shown) on the outlet of the fuel supply pump 103, or both ofthe common rail 106 described below and the fuel supply pump 103.

This is because, by the one way valve, the fuel can be only fed from thefuel supply pump 103 to the common rail 106. Therefore, the adversecurrent can be effectively prevented even when the pressure of the fuelcompression chamber 74 is lower than the pressure in the common rail106. Consequently, a one way valve can be effectively preventing adecrease in pressure of the common rail 106.

(3) Common Rail

Furthermore, as shown in FIG. 12, the common rail 106 is connected to aplurality of injectors (injection valves) 110. Preferably, theaccumulated pressure fuel at high pressure by the common rail 106 isinjected into an internal combustion engine (not shown) from each of theinjectors 110.

Furthermore, but not shown in the figure, the amount of discharge fromeach of these injectors 110 is preferably controlled through an injectordriving unit (IDU). The IDU is connected to an electrical controllingunit (ECU) provided as a controller described letter. The IDU is drivenby drive signals from the ECU.

Moreover, a pressure detector 117 is connected to the side end of thecommon rail 106 and a pressure-detection signal obtained by the pressuredetector 117 is preferably sent to the ECU. That is, it is preferable tocontrol an electromagnetic control valve (not shown) and also controlthe drive of IDU in response to the pressure detected when the ECUreceives the pressure-detection signal from the pressure detector 117.

(4) Piston Amplifier

Furthermore, as exemplified in FIG. 13, a piston amplifier (pressureamplifying piston) is constructed of a cylinder 155, a mechanical piston154, a compression chamber 158, an electromagnetic valve 170, and acirculation pathway 157. It is preferable that the mechanical piston 154is equipped with a pressure-receiving portion 152 having a comparativelylarge area and a pressure portion 156 having a comparatively small area.

That is, the mechanical piston 154 housed in the cylinder 155 is pushedand moved by the fuel having a common rail pressure at thepressure-receiving portion 152. The common rail pressure of thecompression chamber 158 is preferably adjusted to one that allows fuelhaving a pressure of approximately 30 MPa to be pressurized by thepressure portion 156 having a comparatively small area to make thepressure of the fuel in the range of 150 to 300 MPa.

Furthermore, for pressurizing the mechanical piston 154, a large amountof fuel having the common rail pressure is used. After pressurization,it is preferable to flow the fuel back to the fuel tank or the likethrough an electromagnetic driven overflow valve 170. That is, a majorpart of the fuel having the common rail pressure is pressurized by themechanical piston 154 and then flows back to the fuel tank or the liketogether with spilled fuel from an electromagnetic valve 180 of the fuelinjection system.

On the other hand, the fuel pressurized by the pressure portion 156 isfed to a fuel injection system (fuel injection nozzle) 163, effectivelyinjected, and combusted.

Therefore, providing the piston amplifier as described above, themechanical piston can be effectively pushed by the fuel having a commonrail pressure without excessively increasing the size of the commonrail.

That is, as illustrated in the schematic diagram of FIG. 14, accordingto the APCRS system, a mechanical piston is equipped with apressure-receiving portion having a comparatively large area and apressure portion having a comparatively small area. While consideringthe stroke of the mechanical piston, it is possible to effectivelypressurize e fuel having the common rail pressure to a desired levelwith a small pressure. More concretely, the fuel from the common rail(pressure: p1, volume: V1, work load: W1) can be received by apressure-receiving portion having a comparatively large area and thenchanged to higher-pressure fuel (pressure: p2, volume: V2, work load:W2) by a mechanical piston equipped with a pressure portion having acomparatively small area.

(5) Fuel Injection System

Furthermore, the configuration of the fuel injection system (fuelinjection nozzle 110) 166 is, but not specifically limited to,preferably constructed as follows: As shown in FIG. 13, for example, thefuel injection system 166 comprises a nozzle body 163 including a seatsurface 164 on which a needle valve body 162 can be placed, and aninjection hole 165 formed on the downstream side from the valve bodyabutting portion of the seat surface 164. Preferably, it is constructedthat the fuel supplied from the upstream side of the seat surface 164 atthe time of lifting a needle valve body 162 is introduced into theinjection hole 165.

Furthermore, such a fuel injection nozzle system 166 is preferably of anautomatic opening and closing type, capable of lifting the needle valvebody 162 by means of hydraulic pressure of the fuel sent from theupstream side. In this period, the needle valve body 162 is alwaysenergized toward the seat surface 164 by the spring 161 and opens andshuts the needle valve body 162 by switching energization/noenergization of solenoid 180.

Furthermore, as to a time chart of high-pressure fuel injection, it ispreferable to indicate a fuel injection chart having two-stagedinjection conditions as indicated by the solid line as exemplified inFIG. 15.

This is because such a two-stage injection timing chart can be attainedby a combination of the common rail pressure and amplification with apiston amplifier (pressure amplifying piston), and thus the combustionefficiency of fuel can be raised, while cleaning an exhaust gas.

Furthermore, according to the present invention, it is also preferableto indicate a fuel injection chart as indicated by the dashed line B inFIG. 15, a combination of the common rail pressure and amplificationwith a piston amplifier.

By the way, when the piston amplifier is not used, the conventionalinjection timing chart becomes a single-stage injection timing chartwith a low injection amount as indicated by the dashed line C in FIG.15.

(6) Movement

Next, the fuel supply pump 103, the actions of the piston amplifier 108,and the fuel injection system 166 in the present embodiment will bedescribed with reference to FIGS. 12 and 13. That is, as shown in FIG.12, at the time of operating the fuel injection system (fuel injectionnozzle 110) 166, the fuel in the fuel tank 102 is supplied from the feedpump 104 to the fuel supply pump 103. Furthermore, the high-pressurefuel is preferably supplied from the fuel supply pump 103 to the highpressure channel 107 under pressure.

Subsequently, as shown in FIG. 13, the fuel is subjected to pressureaccumulation at approximately 50 MPa in the common rail 106 and then thefuel is preferably pressurized under ultra-high pressure conditions of150 MPa or more as the piston amplifier 108 is provided between thecommon rail 106 and the fuel injection valve 110.

In the present embodiment, an extremely high flow rate of fuel is usedfor operating the piston amplifier 108. Therefore, as an example shownin FIG. 13, the plunger barrel and the pump housing provided in the fuelsupply pump effectively function.

That is, the projection for supporting the upper end of the returnspring is provided in the plunger barrel instead of being provided inthe pump housing, allowing the inner peripheral surface of the pumphousing to be processed precisely and easily. As a result, because thecam shaft can be set at a higher rotational frequency, a high flow rateof fuel that is sufficiently pressurized is allowed to be supplied intoan accumulator. Consequently, for example, the high-pressurization of anAPCRS (Amplified Piston Common Rail) becomes possible. In addition, highpower of a diesel engine, improvement in fuel consumption, reduction inparticulate matters, and so on can be attained.

Industrial Applicability

According to the fuel supply pump of the present invention, theprojection is constructed so as to support the upper end of the returnspring. Thus, a projection for supporting the upper end of the returnspring in the inner peripheral surface of the pump housing is notrequired.

Furthermore, the inner peripheral surface of the pump housing can beprocessed easily and precisely. Therefore, the cam shaft can be set at ahigher rotational frequency. Thus, a high flow rate of fuel that is moresufficiently pressurized than a conventional one can be supplied into anaccumulator. Consequently the high power of a diesel engine, improvementin fuel consumption, reduction in particulate matters, and so on can beattained.

1. A fuel supply pump comprising: a pump housing having a cylindricalspace opened from end to end in the vertical direction; a plunger barrelinstalled in the upper opening portion of the pump housing; a plungerfor pressurizing fuel, installed in the plunger barrel and thecylindrical space of the pump housing so as to be allowed to move up anddown; a cam installed in rotation way below the plunger and integratedwith a cam shaft inserted into the pump housing; a tappet structure bodyinstalled between the cam and the plunger and provided for transmittinga upward or downward movement of the cam caused by the rotation of thecam shaft to the plunger; and a return spring for setting lowering forceto the plunger, installed between the tappet structure body and theplunger barrel, wherein the plunger barrel has a projection forsupporting the upper end of the return spring.
 2. The fuel supply pumpas described in claim 1, wherein the plunger barrel has a large diameterportion for restricting the movement of the return spring in the radialdirection.
 3. The fuel supply pump as described in claim 1, wherein theprojection of the plunger barrel has an outer peripheral surface fittedto the peripheral surface of the cylindrical space of the pump housing.4. The fuel supply pump as described in claim 3, wherein the plungerbarrel has a seal ring receiver in the outer peripheral surface of theprojection.
 5. The fuel supply pump as described in claim 1, furthercomprising: a spring sheet having an opening portion for penetrating theplunger there into is provided between the return spring and the tappetstructure body: and a spring holding portion for restricting thedownward movement of the return spring is provided in the outerperipheral surface of the spring sheet.
 6. The fuel supply pump asdescribed in claim 1, wherein the tappet structure body further includesa cylindrical shell having an outer peripheral surface fitted to theperipheral surface of the cylindrical space of the pump housing and theinner peripheral surface of the shell is provided with an projection forrestricting the movement of the return spring in the radial direction.7. The fuel supply pump as described in claim 1, wherein the fuel supplypump is used in an accumulator fuel injection device for pressurizingfuel at a flow rate of 500 to 1,500 litters per hour to a value of 50MPa or more.